This invention relates in general to a yoke adjusting apparatus for use with a color television picture tube having a funnel and a mating faceplate.
Conventionally, the funnel of a color television picture tube has a neck attached to a flared portion ending in what is generally termed a mouth, to which the faceplate is attached. The neck contains an electron gun assembly for emitting three streams of electrons which excite a phosphor screen deposited on the faceplate. A yoke is provided for insuring that the stream of electrons will impinge on the phosphor screen at the exact location desired for proper convergence. The yoke is composed of four coils of wire which magnetically deflect the electron beam and is held in a yoke mount.
The yoke and yoke mount are attached to and surround the neck of the color television picture tube adjacent to the flared portion of the funnel. After the yoke is positioned on the neck of the funnel it is necessary to tilt the yoke until the desired alignment of the stream of electrons is achieved. A prior art method of tilting the yoke is to position discrete wedges between the yoke mount and the funnel. These wedges are moved about until the yoke is in its desired position. When the alignment of the yoke is complete, the wedges are cemented to the funnel. This poses a tremendous problem in readjusting the yoke at a later date, which may be necessary due to aging of the tube or any vibrations to which the tube may be subjected.
An apparatus for holding a yoke in a desired relationship with a tube is disclosed in U.S. Pat. No. 3,786,185 to Shrader, wherein a platform with projections is adhered to a tube funnel and wherein a yoke housing has indentations. Each of the projections is within and spaced from each of the indentations. In one embodiment an adhesive material is inserted between the projections and the indentations. In an alternative embodiment the projections are threaded and an adjustment means on the yoke housing engages the threaded projections.